1. Field of the Invention
The present invention relates to methods of recycling the components of composite articles and materials comprising hydroxy-phenoxyether polymers to facilitate reuse of such components.
2. Description of the Related Art
Polymeric materials are used widely in many industries, including the packaging industry and the textiles industry. Recycling of plastics has increased greatly over the past decade in response to largely environmental concerns such as diminishing landfill space. This has created a demand for materials and methods which allow for recycling and reuse.
One special issue which arises is that presented by use of multiple materials in a single item. In the packaging industry, a container may comprise more than one type of plastic. For example, it is known to include layers of certain polymers within thin-walled food and beverage containers comprised primarily of PET as a barrier against the unwanted transmission of gases such as oxygen and carbon dioxide. One example of such barrier containers are those described in WO 99/20462, entitled Barrier Coated Polyester. In order to efficiently recycle the materials used in such items, methods used for recycling should be able to separate the recycled item into its component materials so each may be reused.
The disclosed methods of recycling the components of articles such as barrier containers and composite packaging materials comprising hydroxy-phenoxyether polymers facilitate reuse of the hydroxy-phenoxyether polymer as well as the other components such as polyethylene terephthalate and cellulose. According to preferred embodiments, the recycling methods use water as the primary solvent and also use common acids and bases, making such methods highly efficient from the standpoint of materials costs. In preferred embodiments, the methods are environmentally conscious in that they use materials that are generally safe to handle, and that the waste produced in preferred embodiments is essentially neutral and aqueous allowing for recycling or disposal with little negative environmental impact.
In accordance with one embodiment, there is provided a method of obtaining recycled hydroxy-phenoxyether polymers from articles comprising hydroxy-phenoxyether polymers. The method comprises providing an article comprising a hydroxy-phenoxyether polymer, and contacting the article with an aqueous solution comprising 1-50% acid by weight to at least partially dissolve the hydroxy-phenoxyether polymer to form an acidic hydroxy-phenoxyether polymer solution. The method continues with separation of the acidic hydroxy-phenoxyether polymer solution from any solids present, addition of a base to the acidic hydroxy-phenoxyether polymer solution to form a hydroxy-phenoxyether polymer precipitate, and separation of the hydroxy-phenoxyether polymer precipitate. In a preferred embodiment, the aqueous solution comprises 5-20% acid by weight. The method may further comprise one or more of the following: cleaning and/or processing the article into smaller pieces; rinsing and/or drying the hydroxy-phenoxyether polymer precipitate following its separation; and processing the hydroxy-phenoxyether polymer precipitate by pelletizing, pulverizing, grinding, extrusion, molding, or compounding.
In accordance with another embodiment of the present invention, there is provided a method of isolating a hydroxy-phenoxyether polymer from a composite material. The method comprises providing a composite material, contacting the composite material with an aqueous solution having a pH below about pH 4 to form dissolved hydroxy-phenoxyether polymer, separating the dissolved hydroxy-phenoxyether polymer from what remains of the composite material, adding a base to the dissolved hydroxy-phenoxyether polymer in a quantity sufficient to raise the pH to at least pH 6, and isolating the hydroxy-phenoxyether polymer precipitate which forms as a result of the addition of the base.
In accordance with another embodiment of the present invention, there is provided a method of recycling barrier containers comprising polyethylene terephthalate and hydroxy-phenoxyether polymer. The method comprises processing the barrier containers into smaller pieces, contacting the pieces with an aqueous solution having a pH below about pH 4, thereby forming a mixture comprising acidic hydroxy-phenoxyether polymer solution and polyethylene terephthalate pieces, separating the polyethylene terephthalate pieces from the acidic hydroxy-phenoxyether polymer solution, precipitating the acidic hydroxy-phenoxyether polymer solution by adding an alkaline material until the pH has been raised to at least pH 6, and isolating the hydroxy-phenoxyether polymer precipitate. In one preferred embodiment, the aqueous solution has a pH at or below pH 3.5.
In accordance with another embodiment of the present invention, there is provided a method of recycling articles comprising cellulose fiber and hydroxy-phenoxyether polymer, contacting the article with an aqueous solution having a pH below about pH 4, thereby forming a mixture comprising aqueous hydroxy-phenoxyether polymer and cellulose fiber, separating the cellulose fiber from the aqueous hydroxy-phenoxyether polymer, raising the pH of the aqueous hydroxy-phenoxyether polymer to at least pH 6, thereby precipitating at least some of the hydroxy-phenoxyether polymer, and isolating the precipitated hydroxy-phenoxyether polymer. In one preferred embodiment, the aqueous solution has a pH at or below pH 3.5.
In accordance with another embodiment of the present invention, there is provided a method of obtaining recycled hydroxy-phenoxyether polymer solution from articles comprising hydroxy-phenoxyether polymers. The method comprises providing an article comprising a hydroxy-phenoxyether polymer, contacting the article with an aqueous solution having a pH below about pH 4 to at least partially dissolve the hydroxy-phenoxyether polymer to form an acidic hydroxy-phenoxyether polymer solution, and separating the acidic hydroxy-phenoxyether polymer solution from any solids or other materials present to isolate the hydroxy-phenoxyether polymer solution.